1. Field of the Invention
The present invention relates generally to a device for deriving a change of time-dependent information. More particularly, the invention relates to such a device in which time-dependent intensity information or time-dependent quantity information of charged particles such as electrons, ions or the like are converted to positional information spatially representing the times involved with the time-dependent information. The present invention further relates to a device for measuring and displaying a light intensity waveform of light whose intensity varies dependent on time.
2. Description of the Prior Art
There have been know some devices for measuring time-dependent changes in charged particles in a vacuum, i.e., time-dependent changes in the number of charged particles, using an electron multiplier. More specifically, the charged particles to be measured are introduced into an electron multiplier and the number of electrons is increased by producing secondary electrons that are liberated upon collision of the charged particles. The electrons are received by an anode and measured by an oscilloscope. According to another arrangement, the charged particles to be measured are caused to impinge on a scintillator and converted thereby into light, which is then detected as an electric signal with a photomultiplier tube (PMT) or the like. The detected electric signal is measured by an oscilloscope.
In either of the above conventional devices, a change in the intensity of the charged particles is merely amplified and detected as an electric signal to be measured with an oscilloscope, without affecting any special conversion process with respect to time. Therefore, intensity changes that can be measured are limited by the response speed of the oscilloscope used. It is impossible at present to measure time-dependent intensity changes less than 30 ps. Even to maintain a response speed of about 30 ps, care should be taken to design the layout of signal lines and select circuit components. It is therefore not, easy to measure time-dependent intensity changes less than 30 ps.
There has been proposed an arrangement based on the principles of a streak tube for a higher response speed, as shown in FIG. 1 of the accompanying drawings. In FIG. 1, two deflection plates 2, 3 are disposed in a path 1 of the charged particles (photoelectrons) to be measured, and a ramp voltage synchronous with the introduced electrons is applied between the deflection plates 2, 3 to convert a time-dependent change in the intensity of the photoelectrons into positional information on an input surface of a microchannel plate 4. The positional information can be visually recognized as light intensities on a phosphor surface 5. The proposed arrangement is effective to increase the response speed greatly compared with the conventional devices.